Conventionally, electronic devices often have included fans for cooling electronic components in the electronic devices. The fans installed in electronic devices suppress heating of the electronic components caused by operations of the electronic devices or a surrounding environment, for example. Therefore, fans can prevent failure of electronic devices due to overheating, and prevent potential burn injury and other accidents of a user who might touch the overheated electronic devices.
In recent years, the number of electronic components has increased due to electronic devices coming to have various functions. Furthermore, pressure loss has increased as the electronic devices become downscaled. To cope with these conditions, a fan is forced to be rotated more, and a noise caused by operation sound of a fan has become an issue. Thus, for an electronic device to which silence is expected, it is preferable to consider an appropriate cooling system design, an appropriate selection of a fan, and appropriate control, e.g., the revolution frequency, of the fan.
As a mode for implementing a method of predicting noises attributable to a fan in an electronic device, a noise is predicted based on a sound pressure level at a position one meter away from the air-suctioning side of the fan being rotated at unloaded and rated revolution frequencies, which are provided by the manufacture of the fan and the like. As another mode for predicting a noise caused by a fan in an electronic device, a prediction is made based on a loaded noise at an operating point.
In a recent technology, a thermal analysis is applied to predict a pressure difference between the front and the rear sides of a fan at an operating point, and a loaded noise and a flow rate at the operating point are predicted based on the loaded noise, the PQ characteristics, and other factors of the fan. A loaded noise of a fan is a sound pressure level with a load applied to the ventilation channel of the fan. PQ characteristics represent the pressure difference between the front and the rear sides of each fan, that is, a relationship between the static pressure (P) and the flow rate (Q) of the air caused to flow through the ventilation channel when the fan is rotated. A related-art example is described in Japanese Laid-open Patent Publication No. 2001-108642.
However, in such conventional technologies, to predict data about a fan, e.g., a loaded noise and a flow rate of the fan being rotated at a certain revolution frequency, each piece of data including the loaded noise and the PQ characteristics has to be actually measured in advance at each of many rotational frequencies at which a prediction could be possibly be made. Therefore, an enormous number of hours has been spent in performing such actual measurements.
In addition, it is desirable for the loaded noise and the flow rate of a fan to satisfy respective target conditions. In other words, it is desirable to use a revolution frequency of the fan that makes the loaded noise of the fan less than a target loaded noise, and that makes the flow rate more than a target flow rate. To explain the relationship between a loaded noise and a flow rate, reduction in the revolution frequency of a fan lowers a loaded noise of the fan but also lowers the flow rate of the fan. Increasing the revolution frequency of a fan boosts the flow rate but also involves increased loaded noise of the fan. In this manner, a loaded noise and a flow rate of a fan are in a trade-off relationship upon satisfying their target conditions. A prediction can be made as to whether a fan can satisfy both target conditions of the loaded noise and the flow rate, which are in such a trade-off relationship, and the prediction results can be used in designing an electronic device in which the fan is installed. As a method for making such a prediction, the following approach is possible. For example, it is possible to actually measure the loaded noise and the PQ characteristics at every typical revolution frequency of the fan, to store the actual measurements in an associated manner, and to use the actual measurements in predicting a loaded noise and a flow rate. Even upon predicting whether a fan can satisfy both target conditions of the loaded noise and the flow rate, that is, upon making a prediction on data about the fan, an enormous number of hours is spent in making actual measurements because each piece of the data is measured at each of the rotational frequencies of the fan.